1. Field of the Invention
The present invention relates to a cabinet. More particularly, the present invention relates to an outdoor cabinet for housing communications equipment, which includes a thermal regulating system to maintain an internal temperature of the cabinet within prescribed limits.
2. Description of the Related Art
There are many types of optical and electronic equipment that must be located in an outdoor environment. For example, telecommunication equipment, networking equipment, and cable television equipment (generally referred to as “communication equipment”) are often housed in an enclosure or cabinet located outdoors. In the communications industry, such equipment is often referred to as “outside plant equipment”. Outside plant equipment can include such items as amplifiers, splitters, digital subscriber line access multiplexers (DSLAMs), surge protectors, backup batteries, etc.
It is essential that such equipment be operated within a prescribed temperature range and be protected from outside environment contaminates (e.g., water, dust, dirt, sand, insects, rodents). To this end, outdoor cabinets have been developed to house such communication equipment in a highly weather-tight and sealed manner.
Such equipment is known to generate a great deal of heat, especially when a piece of equipment includes a laser, as is the case with many fiber optic devices. This heat must be dissipated to ensure proper operation of the equipment and to prolong the life of the equipment. If the equipment is tightly sealed, a heat dissipating system needs to be employed.
Further, in many environments the cabinets, housing such equipment, are subjected to radiant heat from direct sunlight and light reflected from ground surfaces or adjacent buildings. Radiant heat sources can also greatly increase the interior temperature of the cabinet, which further exacerbates heat problems related to equipment operation.
There are air conditioning systems available in the prior art that may be used in conjunction with outside plant equipment cabinets to aid in maintaining a constant temperature environment for the internal communications equipment. However, an air conditioning system may not be cost effective for all applications. The initial cost of an air conditioning system is high. Further, an air conditioning system consumes a lot of power, takes up space within the cabinet, produces noise and requires periodic maintenance and charging.
An alternative approach has been suggested in several prior U.S. Patents, wherein a heat exchanger is employed to exchange heat between the “internal air” of the cabinet and the “external air” of the environment. The heat exchanger maintains a physical separation between the internal and external air flows so as to prevent contamination of the equipment within the cabinet. U.S. Pat. Nos. 5,570,740; 5,603,376; 5,832,988; 6,119,768, 6,164,369; 6,317,320, 6,494,252 and 6,749,498, all of which are herein incorporated by reference, disclose outdoor equipment cabinets with heat exchangers for cooling internal communication equipment.